Evaporated fuel treatment apparatus

Abstract

An evaporated fuel treatment apparatus is provided for reducing a refilling time, ensuring satisfactory adsorption/desorption performance for an evaporated fuel, and reducing the manufacturing cost through a simplified structure. The evaporated fuel treatment apparatus comprises a casing having formed therein a first chamber in communication with the fuel tank, a second chamber in communication with the first chamber, and a third chamber in communication with the second chamber and the atmosphere. Active carbons are contained in the first chamber and second chamber for adsorbing fuel components in an evaporated fuel introduced from the fuel tank. An adsorbent is contained in the third sub-chamber for adsorbing fuel components in the evaporated fuel introduced from the second chamber. The adsorbent has an air-flow resistance which is set smaller than that of the active carbons.

What is claimed is:  
     
       1. An evaporated fuel treatment apparatus for introducing an evaporated fuel generated in a fuel tank of an internal combustion engine to discharge the evaporated fuel to an intake passage, and emitting the evaporated fuel to the atmosphere after adsorbing fuel components contained in the evaporated fuel, said apparatus comprising: 
       a main chamber and a sub-chamber, wherein the main chamber is in communication with said fuel tank, and the sub-chamber is in communication with said main chamber and the atmosphere, respectively;  
       a main adsorbent contained in said main chamber for adsorbing fuel components in an evaporated fuel introduced from said fuel tank; and  
       a sub-adsorbent contained in said sub-chamber for adsorbing fuel components in the evaporated fuel introduced from said main chamber before said evaporated fuel is emitted from said sub-chamber to the atmosphere,  
       wherein said sub-chamber including said sub-adsorbent has an air-flow resistance which is smaller than an air-flow resistance of said main chamber including said main adsorbent,  
       and wherein said sub-adsorbent is formed in a honeycomb shape formed by a large number of partition walls, and each of said partition walls comprises two spaced apart sheets each having an air permeability, and a large number of granular adsorbents sandwiched between said two sheets.  
     
     
       2. An evaporated fuel treatment apparatus for introducing an evaporated fuel generated in a fuel tank of an internal combustion engine to discharge the evaporated fuel to an intake passage, and emitting the evaporated fuel to the atmosphere after adsorbing fuel components contained in the evaporated fuel, said apparatus comprising: 
       a main chamber in communication with said fuel tank, and a sub-chamber in communication with said main chamber and the atmosphere, respectively;  
       a main adsorbent contained in said main chamber for adsorbing fuel components in an evaporated fuel introduced from said fuel tank, and  
       a sub-adsorbent contained in said sub-chamber for adsorbing fuel components in the evaporated fuel introduced from said main chamber before said evaporated fuel is emitted from said sub-chamber to the atmosphere,  
       wherein said sub-chamber including said sub-adsorbent has an air-flow resistance which is smaller than an air-flow resistance of said main chamber including said main adsorbent,  
       and wherein said sub-adsorbent comprises a large number of adsorbent sheets each having an air permeability and disposed in said sub-chamber in a manner such that said adsorbent sheets are spaced apart from each other, and arranged in a direction perpendicular to a direction in which the evaporated fuel flows.  
     
     
       3. An evaporated fuel treatment apparatus according to  claim 1  further comprising, 
       a casing having formed therein the main chamber and the sub-chamber, wherein the main chamber is in communication with said fuel tank, and the sub-chamber is in communication with said main chamber and the atmosphere, respectively.  
     
     
       4. An evaporated fuel treatment apparatus according to  claim 2  further comprising, 
       a casing having formed therein the main chamber and the sub-chamber, wherein the main chamber is in communication with said fuel tank, and the sub-chamber is in communication with said main chamber and the atmosphere, respectively.